# Copyright 2020 Zhejiang Lab. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# =============================================================

from typing import Sequence, Callable
from numbers import Number
from kamal.core import exceptions

class AttachTo(object):
    """ Attach task, metrics or visualizer to specified model outputs
    """
    def __init__(self, attach_to=None):
        if attach_to is not None and not isinstance(attach_to, (Sequence, Number, str, Callable) ):
            raise exceptions.InvalidMapping
        self._attach_to = attach_to

    def __call__(self, *tensors):
        if self._attach_to is not None:
            if isinstance(self._attach_to, Callable):
                return self._attach_to( *tensors )
            if isinstance(self._attach_to, Sequence):
                _attach_to = self._attach_to
            else:
                _attach_to = [ self._attach_to for _ in range(len(tensors)) ]
            _attach_to = _attach_to[:len(tensors)]
            tensors = [ tensor[index] for (tensor, index) in zip( tensors, _attach_to ) ]
        if len(tensors)==1:
            tensors = tensors[0]
        return tensors

    def __repr__(self):
        rep = "AttachTo: %s"%(self._attach_to)